built in operator: select

    description:
        select[k1, k2] sp
        select the k1'th to the k2'th elements from the given superposition
        indices start from 1, not 0
        final element has index -1, 2nd last element -2, and so on.

    examples:
        select[2,2] split |a b c d e f g h>
            |b>
        
        select[4,7] split |a b c d e f g h>
            |d> + |e> + |f> + |g>
        
        select[2,-2] split |a b c d e f g h>
            |b> + |c> + |d> + |e> + |f> + |g>
        
        head (*) #=> select[1,1] |_self>
        tail (*) #=> select[2,-1] |_self>
        
            
    see also:
        sselect

Home